Apple’s biggest iPhone plant is struggling to return to full production after China’s new year holiday because of restrictions on worker movement caused by the coronavirus, adding to concerns that the outbreak will have a lasting effect on the US company.

Contract manufacturer Foxconn assembles many of Apple’s newest iPhones at a huge factory complex at Zhengzhou in China’s Henan province. At full production, more than 200,000 workers put together iPhones on its assembly lines.

But Foxconn faces multiple challenges to staffing the factory, which has partially resumed production as workers trickle back from an extended holiday break. On Tuesday, the unit responsible for iPhone production stopped accepting workers from outside the city, pointing to issues in housing workers in need of quarantine.